Boom assemblies are generally used in the agricultural industry for spraying liquids, such as herbicides, insecticides, and pesticides. Typically, the boom assemblies are attached to farm vehicles adapted to traverse cultivated fields having varying contours. More particularly, the boom assemblies comprise a number of aligned sprayers in communication with a tank of liquid transported by the farm vehicle. The booms are used for spreading the liquid along a substantially wide path provided by the movement of the farm vehicle. Two boom assemblies are generally connected to the rear of the farm vehicle, such that a first boom assembly extends outwardly to the left of the farm vehicle and a second boom assembly extends outwardly to the right of the farm vehicle.
The desire to have the boom assemblies cover a significant area of the field during the application of the liquid has resulted in the construction of lightweight boom assemblies using a lattice framework. Accordingly, common booms extend from twenty to twenty-five feet in total length. Using lightweight materials to construct the boom assemblies has decreased the durability of the boom. Consequently, a boom can suffer extensive damage, if the boom assembly comes in contact with an intrusive obstacle or abutment such as a tree, rock, or post.
Prior to the use of boom breakaway assemblies, booms were susceptible to irreparable damage or breakage when encountering an unforgiving object in the field. Boom breakaway assemblies allow the boom to give or break away when coming in contact with an object, thereby preventing damage to the boom. Generally, a boom breakaway assembly utilizes an outer boom portion pivotally connected to an inner boom portion. The pivot permits the outer boom portion to horizontally pivot in response to contact by an object. Additionally, the outer boom portion (or the middle and outer boom portions) may be capable of pivoting vertically to overcome an obstacle in its path.
Not only is the boom capable of pivoting away from the intrusive object, the boom is often capable of automatically returning to a desired outward position once the boom has cleared the intrusive object. More specifically, a spring or coil is used to return the outward boom portion to a desired outward position (e.g., perpendicular to the travel of the farm vehicle) after the boom has cleared the obstacle.
Typical boom breakaway assemblies, however, require a high holding force to keep proper tension on the breakaway joint, to minimize undesired motion of the boom parts during use. The high holding force, generally provided by a spring or coil, remains constant even after the outward boom portion comes in contact with an obstacle in the field. Consequently, damage can occur to the boom structure until the obstacle is cleared. Although the spring permits the outer boom portion to breakaway during contact with an obstacle, the spring continues to exert a holding force (e.g., an effective spring rate) on the outer boom portion, thereby attempting to return the outer boom portion to the desired outward position. Such constant holding force increases the impact force during the entire contact period with the obstacle-effectively dragging the outer boom portion over the obstacle.
What is needed is a boom breakaway assembly that quickly and temporarily reduces the holding force of a bias (or the effective spring rate of a spring) until the outer boom portion clears an intrusive object. It is to such a device that the present invention is primarily directed.